Jen is a young male Gelfling and the protagonist of the film; raised by the urRu, and therefore both deliberate and impatient. Jen wears a pale, cream-colored tunic. His skin has a brown complexion and his hair is dark with fair (almost silver) streaks, and grows to shoulder-length. He carries a flute around his neck, which he is shown playing at intervals, and an urRu token known as a firca.[1]

His creature and costume design were provided by Brian Froud and his designer and fabrication supervisor was Wendy Midener.

Kira survived the slaughter of her people, the Gelflings, because she was hidden by her mother in a hollow tree trunk. Taught by the Podlings, Kira learned to converse with wild animals and is given to wandering the swamps outside the Pod village, accompanied by Fizzgig. She is soft-spoken and gentle as a rule. Kira wears a golden-brown dress and a brown cloak. She has a fair complexion and her hair is long and fair, almost white. As a female Gelfling, Kira has segmented bat-like wings that unfold from her shoulders on command: a physical feature not shared by male Gelflings.[2] Although not shown in flight, she is twice seen using these wings to slow a fall.

Described as "... a friendly monster" in the initial draft of the screenplay, the character of Fizzgig is the pet of Kira: resembling a domestic dog in voice and manners, but unlike a dog in that his facial features are tiny and his entire body is represented by a brown/red/gray ball of fur. Fizzgig moves by rolling, though he does appear to have at least two legs. His mouth, when open, appears to encompass most of his size and possesses two sets of sharp teeth. He is fiercely loyal to Kira, has an aggressive temper, and is wary of unfamiliar things. Fizzgig is at first wary of Jen, but becomes his friend. The name of Fizzgig's species is not mentioned, nor are any more of his kind seen, although Fizzgig's species are said to be native to Thra. Fizzgig is the only major character represented in the movie by a puppet with immobile eyes. Fizzgig later made a cameo in the Fraggle Rock episode "Gobo's Discovery", as one of the background cave creatures.

Aughra is an Oracle and the sole member of her (unidentified) species. A keen astronomer, she maintains an observatory upon a cliff atop a mountain, known as High Hill, which houses an enormous, working orrery that shows all the worlds orbiting Thra's Three Suns; the latter associated with her prediction of the Great Conjunction. Aughra is portrayed primarily by Frank Oz in a costume. Oz also voiced Aughra originally (similar to a combination of Fozzie Bear, Yoda, and Miss Piggy); but her lines were re-dubbed by Billie Whitelaw.

According to the book The World of the Dark Crystal, Aughra is an emanation of the planet Thra, meant to record the varieties of life before re-absorption into the planet's crust. Her exact age is not given; but she is described witnessing the arrival of the urSkeks, and later their separation into Skeksis and urRu. The novelThe Dark Crystal mentions that Aughra is both male and female, whereof only the female is active. Among other abilities, Aughra is capable of bidding plants to move, and can remove her single remaining eye from its socket and hold it in one hand for extended view, or place it in another location and move it by mental command. Her brisk voice is harsh, broken, and short of breath. The novel describes her breath as "loud, rasping, rheumy, and [having] a dank stench". Dialogues featuring her suggest a capricious manner: when Jen tries to explore her tools, she orders him 'not to touch anything' and ignores having done so, and is shown saying dramatically that "the Great Conjunction is the end of the world", and then adding, in a different tone of voice, "or the beginning! Hmf!" before dismissively remarking that "ends and beginnings [are] all the same". She seems well-acquainted with phenomena most of Thra's inhabitants would view with awe, but is herself overawed when the urSkeks assume their true forms. When she asks Jen the location of his urRu mentor, and hears that the latter is dead, she becomes wary and says "Could be anywhere, then". Contrastingly, she appears blasé toward her own death. When facing the Skeksis, she rebukes them for pillaging her home, calling them "fools" and the Garthim "stupid", and adding: "You want Gelfling? Why not ask me? No; easier to send your crab-brained soldiers, burn my home!". Aughra was allegedly to appear in the sequel to The Dark Crystal, titled The Power of the Dark Crystal,[3] though Jim Henson's daughter Cheryl mentioned in September 2011 that the sequel was on hold.[4] Her designer was Brian Froud and her Design and Fabrication Supervisor was Lyle Conway. The Fabrication Team for Aughra were David Barclay, Jeremy Hunt, Paul Jiggins, Graeme Galvin, and Steve Court.

Gelflings are slender humanoid beings with pointed ears and protracted facial structures who originally populated much of the world of Thra. Their hands have three long fingers and a thumb. Female Gelflings have bat-like wings that can be folded to fit easily under clothing. These wings can be used to slow a long fall to allow for a safe landing, even with the added weight of a second Gelfling holding onto the first. The Marvel Comics adaptation of the movie states that in the past, females could fly; but the wings have become vestigial.

The Gelflings once had a flourishing civilization, as seen in the film, and had a system of writing similar to hieroglyphics. Jen and Kira are the only known survivors of a massacre masterminded by the Skeksis. Upon physical contact with one another, Gelflings can share thoughts, memories, and emotions by a process called dreamfasting. [5] Other Gelflings had been introduced in the Dark Crystal universe, but only for Tokyopop's OEL manga Legends of the Dark Crystal: English rock band Kasabian released a song called "gelfling" as a b-side to the single "bumblebeee".

The urRu/Mystics are benevolent, hunchbacked counterparts of the malevolent Skeksis (see below). Whenever one member of either race dies or is injured, his counterpart in the other is similarly affected. The urRu have four arms, elongated heads, white hair, and tails, in a manner that concept artistBrian Froud described as being "... between a dog and a dinosaur". The urRu are also called 'Mystics' or "chanters". There are ten urRu at the beginning of the film:

The Skeksis are the antagonists of the film: the ten "evil" versions of the ten "good" urRu (see above). The word "Skeksis" serves as both singular and plural form for this species, with the singular pronounced /ˈskɛksɪs/ and the plural /ˈskɛksiːz/. They are described by concept artistBrian Froud as "... part reptile, part predatory bird, part dragon". Like their urRu counterparts, they have four arms; but in the Skeksis the two lower arms have become weak and atrophied, and are rarely seen. The Skeksis have kept themselves from dying of old age by draining the vitality from other beings. In the film, the Skeksis are represented by puppets engineered under the direction of Jim Henson. Jim Henson has said that in the development of the Skeksis, the creators drew inspiration from the Seven Deadly Sins, in that each Skeksis represents a different kind of evil, such as cruelty, selfishness, greed, unchecked ambition, treachery, and wrath.

The Skeksis were full-bodied puppets operated in a very similar way to Big Bird. The puppeteer's secondary arm was in the arm of the Skeksis and the puppeteer's primary arm was held up over the puppeteer's head and the hand operates the jaw. A monitor inside the suit allowed the puppeteer to see.

skekZok the Ritual-Master (performed by Jim Henson and voiced by Jerry Nelson) - The Court High priest, governing the others by prophecies and rites invented by himself. Second-most-powerful after the various Emperors.

skekSil the Chamberlain (performed by Frank Oz and voiced by Barry Dennen) - Exiled after unsuccessfully challenging skekUng's claim to the throne; later reinstated after he captures Kira.

skekTek the Scientist (performed by Steve Whitmire) - A mad scientist performing unspecified deadly experiments on animals, and deriving 'essence' from Gelflings and Podlings to rejuvenate his compatriots. Destroyed by his prisoners at the behest of Kira and Aughra.

skekAyuk the Gourmand (performed by Louise Gold and voiced by Thick Wilson) - Commander of slaves to create complex meals for the Skeksis. He represents the Deadly Sin of Gluttony.

The UrSkeks are the original species from which the urRu and the Skeksis are derived. They are seen when the Dark Crystal is made whole, whereupon they are depicted as tall, luminescent beings of vaguely Gelfling-like shape. They sported large craniums and slim bodies. Only eight appeared in the end of the film, with UngIm as their representative. They include:

SoSu - The combined form of Emperor skekSo + Master urSu. Both died of old age.

TekTih - The combined form of Scientist skekTek + Alchemist urTih, both burned to death

TokyoPop's Legends of the Dark Crystal Vol.1 introduces two new Skeksis (SkekLach the Collector & SkekVar the General), and one new Mystic (urSen the Monk), producing:

LachSen - The combined form of SkekLach the Collector + urSen the Monk

SkekVar's counterpart is not introduced in vol. 1. It is expected volume 2, which is scheduled for publication in August 2010, and is due to include more new Skeksis and Mystics.[citation needed]

In the Dark Crystal Author Quest, the new urRu and new Skeksis are counterparts, resulting in yet another UrSkeks:[6]

MalVa - The combined form of SkekMal the Hunter and urVa the Archer.

According to The World of the Dark Crystal, the UrSkeks originated on a world where moral imperfections were found intolerable, from which 18 of their species, led by SoSu, were banished from their native world to Thra through the Crystal of Truth. Once on Thra, they befriended Aughra, and later attempted to use the next Great Conjunction to destroy their imperfections, and thus created the Skeksis, commanded by skekSo and the urRu led by urSu. In the resulting struggle, the Crystal was damaged, and the urRu abandoned the Castle. If any member of either species is wounded or killed, an equivalent suffers the same in the other. When the story begins, both skekSo and urSu perish, leaving skekUng and urIm to succeed them. At the climax, the UrSkeks are reformed, and depart into a higher level of existence. Because skekTek was killed during the course of the film, destroying his urRu counterpart urTih, the UrSkek 'TekTih' never appeared.[7]

The Podlings are a race of gentle "earth-people" native to Thra and affiliated with the Gelflings; named for the giant seed-pods in which they live. [8] The Podlings are dwarf-like in stature yet with very rounded, circular-shaped, bulbous heads and small round eyes. They have a love of music and parties. In tune with nature, they can speak to animals and beasts and teach the Kira this trait. One of the most important Podlings is Ydra, the adoptive mother of Kira.

Many of the Podlings are either killed, or kidnapped by the Skeksis by whom they are used as slaves. Being drained of a vital 'essence' by SkekTek, the Podling slaves of the Skeksis appear withered, and their hair has turned white or fallen away. At the end of the film, the Podlings regain most of their youth and knowledge. According to The World of the Dark Crystal by Brian Froud, many Podlings were lured to the Castle of the Crystal by the Skeksis.

The Garthim are crustacean-like creatures employed by the Skeksis as soldiers (designer Brian Froud has claimed a fascination with lobsters): protected by a tough exoskeleton or carapace, who shamble on tentacles and brandish crab-like claws. The Garthim also appear to be at least partly mechanical in structure. Their eyes glow purple and appear related to the Dark Crystal. In the film, they are destroyed immediately following the Conjunction and the healing of the Crystal, disintegrating along with the black stone that coats the castle's silver walls. According to The World of the Dark Crystal by Brian Froud, the Skeksis created the Garthim in imitation of "sea creatures" native to the urSkeks' world, for the sole purpose of taking or killing prisoners.

The Conceptual Designer for the Garthim was Brian Froud and the Design and Fabrication Supervisor was Fred Nihda.

The Crystal Bats are winged creatures similar to bats, but with stick-like bodies, which act as spies for the Skeksis. According to The World of the Dark Crystal by Brian Froud, the Crystal Bats were bred by the Skeksis to carry lenses of artificial crystal that sent images of all they saw back to the Crystal in the Skeksis' castle. Two are seen spying on Jen and Kira.

Landstriders are quadrupeds native to the forests of Thra, having white skin, vaguely anteater-like faces, long ear-like appendages, and extremely long and powerful limbs with which they move very fast over vast distances. They are ridden by Jen and Kira in the film, and identified by Froud as regular mounts of Gelflings. Landstriders are very tough and their limbs can be used as formidable weapons. As a result, Landstriders are perhaps the only natives of Thra able to oppose the Garthim. In the production of "The Dark Crystal," the Landstriders were performed by professionals operating on four stilts. The Landstriders were performed by Robbie Barnett, Swee Lim, and Hugh Spight.

The Nebrie are large grub-like creatures that have some amphibian qualities. The Nebrie dwell in marshes and swamps. Although they appear menacing the Nebries are not especially aggressive and appear to be vegetarian. A Nebrie infant is seen roasted on the dining table of the Skeksis in the Castle of the Crystal, and the novel depicts Nebries as the Skeksis' food of choice.

The Nebrie was designed by Brian Froud and the Design and Fabrication Supervisors were Tim Miller and John Coppinger.

Many other creatures are seen briefly, including plants able to fly; flowers able to retract their petals; thick tree-like stalks that expand and compress; a gigantic predator that disguises its mouth as a hole in the ground and closes its mouth when prey enter; vine-like or grass-like creatures, able to move; rodent-like animals; and birds with a large horn instead of a beak, among others.